/Engine/Plugins/Experimental/ControlFlows/Source/ControlFlows/Public/ControlFlowNode.h
Would be nice to not force people to use int32 for the branch key, but finding the syntax to get it to work properly proved to be more difficult than it was worth. End result is callers have to cast to an int32.
typedef TBaseDelegate_OneParam< int32, [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [FControlFlowBranch](API\Plugins\ControlFlows\FControlFlowBranch) > > FControlFlowBranchDefiner